Pushbutton-operated overload switch



July 14, 19.59 J. ELLENBERGER PUSHBUTTON-OPERATED OVERLOAD SWITCH 5 Sheets-Sheet 1 Filed Dec. 2, 1957 JNVfNTOR JACOB ELLEN BERGER PATENTAGENT J. ELLENBERGER PUSHBUTTON-OPERATED OVERLOAD SWITCH July 14, 1959 3 Sheets-Sheet 2 Filed Dec. 2, 1957 BERGER R w W J JACOB "ELLEN Q/flz PATENT AGE Filed Dec. 2, 1957 July 14, 1959 J. ELLENBERGER 2,895,028

PUSHBUTTON-OFERATED OVERLOAD SWITCH O 2 Z O 7 F/6.7 14 43 I 27 O 5 22 JNVfN/OR JACOB ELLENBERGER P TENT AGE NJ 3 Sheets-Sheet s v United States Patent PUSHBUTTON-OPERATED OVERL'OAD SWITCH Jakob Ellenberger, Altdori, near Nurnberg, Germany Application December 2, 1957, Serial No. 699,952

Claims priority, application Germany December 14, 1956 16 Claims. (Cl. 200-88) The present invention relates to a pushbutton-operated thermally released overload switch which is mounted in a housing of a considerably greater length than width.

The switches of this kind known prior to the invention which had a trip-free release and were acted upon by thermal or magnetic functions had the disadvantage that the trip-free release required them to be of a relatively great width so that it was often quite difiicult to install them within a confined space.

It is an object of the present invention to overcome this disadvantage by attaining the trip-free release of the switch by the use of a contact bridge which is freely pivotable on a control bridge which is slidable in the axial direction of the switch control rod.

According to the invention, when the pushbutton of the switch is being depressed, this contact bridge is arrested in a fixed position in engagement with a control spring by means of a carrier member which is mounted on the control bridge and by a projecting portion on an angular part of the contact bridge; This control spring, in turn, is controlled by a thermal and/or magnetic release mechanism, and it may additionally be acted upon manually by a pushbutton. The switch construction may according to the invention be further simplified by making the control spring in the form of a heated bimetallic strip which is preferably heated indirectly. If the switch is also to be provided with an electromagnetic release, the heating coil for this bimetallic strip may be connected in series with the winding of the electromagnet.

Another feature of the invention is to provide the switch with very simple means for adjusting the bimetallic strip to operating currents of diiferent strength. These means consist of an adjusting screw with a conical tip which acts upon a projection on the bimetallic strip to vary the initial tension of the latter. The bimetallic strip is provided with a detent which holds the contact bridge in the on position. This detent is preferably likewise conductive so that, when the switch operates, the circuit will also be broken at this point. Above the mentioned detent, the bimetallic strip may also be provided with a second detent which is adapted to arrest the contact bridge in an intermediate position in which the angular portion thereof may engage with a projecting portion of the switch housing. The control bridge is also provided with a pair of contacts which are operatively associated with other contacts on the base of the switch which, by means of terminal strips, may be connected to signaling circuits. In the intermediate position, however, the new switch will not close any of the signaling circuits and it will also interrupt the main circuit. In this position, the carrier member on the control bridge and the resilient contacts will be electrically separated from each other by the control bridge and insulating bushings.

In order to attain the object of the invention of producing a switch of very small outer dimensions, and particularly of a very narrow width, the bimetallic strip is preferably mounted at a point between the coil of the electromagnetic release mechanism and the contact bridge. The armature of the magnet is provided with a slot into which an angular lever engages which, in turn, may be acted upon by a pushbutton for releasing the switch manually. This slot arrangement permits the switch to be operated independently of the electromagnetic and thermal release.

The switch according to the invention is designed to fit into a narrow oblong housing which consists of two longitudinally separated parts and is provided with internal projections, recesses and webs which are associated with the switch parts to serve as abutments and guiding means therefor.

Further objects, features, and advantages of the present invention will become apparent from the following detailed description thereof, particularly when read with reference to the accompanying drawings, in which-- Fig. 1 illustrates a switch according to the invention in the off position with one part of the housing removed;

Fig. 2 illustrates a cross section taken along line IIII of Fig. 1, but with the entire housing;

Fig. 3 illustrates a view similar to Fig. 1, but with the switch in the on position;

Fig. 4 illustrates another view similar to Fig. 1, but with the switch in the neutral position;

Fig. 5 illustrates a cross section taken along line V-V of Fig. 4, but with both parts of the housing;

Fig. 6 illustrates a diagrammatic view of the switch connections in the on position;

Fig. 7 illustrates a modification of the switch without an electromagnet; while Fig. 8 illustrates one of the two housing parts.

Referring to the drawings, Figs. 1 to 6 illustrate the inventive concept as applied to an automatic switch which is mounted within a flat housing, and in which the release of the switching operation may be carried out either electromagnetically or thermally.

The housing of the switch consists of the two parts 1 and 2. The upper portion 3 of the housing contains a pushbutton 4 with a skirt 5 which is slidably guided within a bore 6. Pushbutton 4 carries integrally there with a control rod 7 which is surrounded by a coil spring 8 which tends to press pushbutton 4 outwardly to its off position. A bridge member 9 of insulating material is connected to the lower end of control rod 7 with a carrier member 10 secured thereto which has on each side an upwardly projecting tab 11. The upper edges 12 of tabs 11 pivotably support an angular lever having two arms 13 and 14. This lever has an inwardly extending projection 15 which, as illustrated in Fig, 1 may be engaged and taken along by member 10 when bridge member 9 is depressed.

The angular lever 13, 14 which forms a contact bridge is pressed upwardly by a coil spring 16 and has a contact point 17 which is operatively associated with another contact 18 on a terminal strip 19 leading to the outside of the housing. Lever 13, 14 which is made of conductive material has another contact point 20 which, when the switch is in the on position, as illustrated in Fig. 3, engages with a detent 21 which is mounted on a latching member in the form of a bimetallic strip 22. This bimetallic strip has another detent 53 which is adapted to engage with lever 13, 14 to hold the same in an intermediate position. Bridge member 9 has mounted on its lower side contact springs 54 which are adapted to make contact either with the pair of contacts 23 or the pair of contacts 24, depending upon the position of bridge member 9. Contacts 23 and 24 are fixed on terminal strips 25 and 26, respectively, which also lead to the outside of the housing. Bridge member 9 and contact springs 54- are separately insulated by bushings 49 and 50.

The bimetallic strip 22 further carries a heating coil 27 which, as illustrated in Fig. 6, is connected to a Winding 28 of an electromagnet 29. Armature 30 of this magnet has in its upper end a slot 31 into which a laterally projecting lug 32 on an angular lever 33 engages which is pivotably mounted at 34. Lever 33 has another lateral lug 48 which is adapted to be engaged by the release button 35. Lever 33 is connected to bimetallic strip 22 in such a manner that, when this lever is rocked about the pivot at 34 by depressing the release button 35, the bimetallic strip will be similarly disengaged from the levers 13 and 14 as it will be if heated by its heating coil 27. The bimetallic strip 22 may thus be actuated not only by the core of the magnet or the flexing of the bimetallic strip 22 under thermal action but also by the release button 35.

For adjusting the switch to the strength of the respective operating current, the bimetallic strip is further provided with a laterally projecting lug 36 upon which the conical tip 37 of a set-screw 38 is adapted to act which is mounted at 3:9 and may be adjusted from the outside of the housing to vary the initial tension of the bimetallic strip.

Winding 28 of electromagnet 29 is connected to a terminal strip 4t) leading to the outside, and is connected in series with the heating coil 27 of bimetallic strip 22 and with contact lever 13, 14.

Terminal strips 25 and 26 are adapted to be connected to signalling means, for example, lamps.

The embodiment of the invention illustrated in Fig. 7 differs from that shown in Figs. l to 6 merely by the omission of the electromagnetic release means 28, 29 and 30.

The operation of the switch is as follows:

When the switch, in the on position as illustrated in Figs. 3 and 6, is connected in a circuit, current flows from terminal 19 via contacts 13 and 17, the angular bridge 13, 14, detent 21, bimetallic strip 22., heating coil 27, and winding 28 of magnet 29 to terminal 40. If the magnetic part of the switch is omitted, as shown in Fig. 7, the connection is made on terminal 41). In this case, the bimetallic strip 22 may be heated directly. In the on position shown in Figures 3 and 6, the two contacts 24 are connected to each other by contact springs 54 so that a signal circuit which is connected to terminals 26 will be closed. If an over-current of a relatively low magnitude passes through the switch, the bimetallic strip 22 will be actuated in the usual manner by flexing the strip to the right. Detent 21 will then slide off contact point 20. Under the action of the two springs 8 and 16, bridge member 9 will then move upwardly to the position shown in Fig. 1. Contact lever 13, 14 will pivot about the rock points 12 to the position shown in Fig. l, and the upper arm 13 will engage the inclined surface 41 of the housing. The two contacts 17 and 18 will then be likewise disengaged so that the circuit will be broken at two places.

The same circuit interruption occurs if the electromagnet 29 is energized by suddenly occurring overcurrents. The armature 30 then acts on lever 31 and rocks the same about its pivot at 34, and its projection 42 then bends the bimetallic strip 22 to the right in exactly the same manner as would occur under the thermal action of the current flowing through heating coil 27. The switch will therefore also in this manner be moved into the off position shown in Fig. 1.

When the switch is in this off position, contacts 23 are connected with each other by the bridging contact springs 54 so that, if a signal circuit is connected to terminals 25, such circuit will be closed.

In order to notify the person in charge of the electric control system that the switch has been tripped, but that this has already been noticed, the switch is further provided with a neutral position in which none of the contacts are closed. This position is illustrated in Fig. 4, in which the contact 17 of the lever 13, 14 will engage a projection 43 on the housing, while contact portion 20 will be arrested by the detent 53 on bimetallic spring 22. The bridging contact springs 54 will then be disposed at a point between contacts 23 and 24 so that none of the signal circuits is closed. The switch can be brought from the off position, shown in Figure l, to the neutral position, illustrated in Figure 4, by depressing the pushbutton 4 to such extent that the top of the skirt 5 is aligned with the upper end of the bore 6. During such limited depression of the pushbutton 4, the lever system 13, 14 is taken along by the carrier member 10, engaging the top end of projection 15 forming part of this lever system 13, 14, as shown in Figure 1. When the lever 13 has arrived at about the position shown in Figure 4-, its contact point 29 has passed the detent 53, so that upon release of the partially depressed pushbutton 4, the spring 8 tends to move this pushbutton 4 upwards. However, such movement is prevented by the engagement of the contact point Ztl with the detent 53 on the bimetallic strip 22 which, in the meantime, has cooled down from previous heating, whereby the tabs 11 projecting from the carrier member 10 act on the lever system 13, 14, i.e., rock the same from the slanting position, shown in Figure 1, to the opposite slanting position, shown in Figure 4. The left end of the detent 53 forms the axis of rotation for the lever system 13, 14 during this rocking movement.

If the switch is to be reclosed from the position, illustrated in Figure 4, it is first necessary to release the switch mechanism by depressing the release button 31, as described before, whereupon the switch mechanism returns to the position shown in Figure 1. From this position, the switch can be closed in the manner delcribed in the foregoing by fully depressing the pushbutton 4.

In order to facilitate the actuation of the switch, the contact point 20 on the lever 13 is provided with an inclined side 44-, adapted to slide along the opposite surfaces on the detents 53 and 21 when the pushbutton 4- is depressed.

It is to be noted that the switch will release when actuated by overloads or short circuits, even if the pushbutton 4 should be jammed in its depressed or on-position (Figure 3), due to a mechanical deficiency, or while manually held in such position. Upon occurrence of an overload or short circuit, the bimetallic strip 22 will be bent, either due to thermal action or by the armature 31 via the lever 33, so that the detent 21, then engaging the contact point 20, will become disengaged from the latter with the result, that the lever system 13, 14 will be brought to the off-position (see Figure 1) under the action of the spring 16, regardless of the retained depressed position of the pushbutton In other words, a free release of the switch mechanism in the event of occurrence of short circuits or overloads is assured, even if the release button 4 should be held or be retained in depressed position.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim 1. An overload switch having a trip-free release comprising a.housing, switch elements provided within said housing and comprising a contact bridge having an angulararm thereon, a control rod, a pushbutton connected to one end of said control rod for moving said switch to the on position, a bridge member rigidly secured to the other end of said control rod, said bridge member having a projection thereon, said contact bridge being freely pivotable on said projection and being slidable along said control rod in the axial direction thereof, a carrier member mounted on said bridge member, a latching member, a projection on said angular arm of said contact bridge, said carrier member being adapted to engage said last projection when said bridge member is moved together with said control rod and pushbutton to move said contact bridge into engagement with said latching member, at least one automatic overload actuated releasing means connected to said latching member for varying the position thereof so as to disengage said latching member from said contact bridge and thereby to move said switch to the oflf position, and a second pushbutton adapted to act upon said latching member for disengaging said latching member from said contact bridge and for manually moving said switch to the oif position.

2. An overload switch as defined in claim 1, wherein said latching member comprises a bimetallic strip.

3. An overload switch as defined in claim 1 wherein said latching member comprises a bimetallic strip and said automatic releasing means comprise a heating coil around said strip.

4. An overload switch as defined in claim 1, wherein said latching member comprises a bimetallic strip and said automatic releasing means comprise an electromagnet adapted to act upon said bimetallic strip.

5. An overload switch as defined in claim 1, wherein said latching member comprises a bimetallic strip and said automatic releasing means comprise a heating coil around said strip and an electromagnet adapted to act upon said strip and connected in series with said heating coil.

6. An overload switch as defined in claim '2, wherein said bimetallic strip has a projection thereon, and an adjusting screw having a conical tip engaging with said projection for adjusting the tension of said strip in accordance with the strength of an electric current to be controlled by said switch. 7. An overload switch as defined in claim 2 further comprising a detent on said bimetallic strip adapted to engage with said contact bridge to maintain said contact bridge in the on position.

8. An overload switch as defined in claim 7, further comprising a second detent on said bimetallic strip above said first detent and adapted to engage with said contact bridge to maintain said bridge member in an intermediate position, said housing having an inner projection, said angular arm on said contact bridge engaging with said inner projection when said bridge member is in said intermediate position.

9. An overload switch as defined in claim 2, further comprising a pair of resilient contacts on said bridge member, a pair of stationary contacts, a second pair of stationary contacts, each pair of said stationary contacts being adapted to be connected to different signaling means, said contacts on said bridge member being adapted to engage with one pair of said stationary contacts when said switch is in the on position and to engage with the other pair of stationary contacts when said switch is in the off position.

10. An overload switch as defined in claim 9 wherein said carrier member and said resilient contacts on said bridge member are electrically separated from each other by said bridge member and insulating bushings.

11. An overload switch as defined in claim 4, wherein said bimetallic strip is mounted between said electromagnet and contact bridge.

12. An overload switch as defined in claim 4, wherein said electromagnet has an armature with a slot near one projecting end thereof, and further comprising an angular lever pivotably mounted and engaging at one side into said slot and at the other side with said bimetallic strip, said second pushbutton being adapted to engage with said last lever to disengage said strip from said contact bridge.

13. An overload switch as defined in claim 1, wherein at least one part of said housing has a plurality of internal projections, recesses, and webs therein to serve as guiding means and abutments in association with the various parts of said switch.

14. An overload switch as defined in claim 1, wherein the inner wall of said housing has an inclined surface opposite said contact bridge, said surface being adapted to serve as seat for said contact bridge when in its ofi position, whereby said contact bridge assumes such inclined position.

15. An overload switch as defined in claim 1, wherein said housing is of narrow oblong shape and comprises two parts joined in a plane through the longitudinal axis of the switch.

16. An overload switch as defined in claim 1, wherein a spring is provided between said bridge member and said contact bridge, said spring biasing said contact bridge in contact opening direction so that said contact bridge is released although said pushbutton is retained in depressed position.

References Cited in the file of this patent UNITED STATES PATENTS 2,409,917 Van Hoorn Oct. 22, 1946 2,443,090 Wise June 8, 1948 2,633,515 Locher Mar. 31, 1953 2,741,681 Allard Apr. 10, 1956 

